Species Invasion Shifts the Importance of Predator Dependence

Griffen, Blaine D.; Delaney, David

doi:10.1890/07-0172.1

Cited by 59 publications

(58 citation statements)

References 48 publications

(68 reference statements)

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“…Corroborating prior studies (Schenk et al 2005;Tschanz et al 2007), we estimated the interference parameter at an intermediate level between the two extreme models (m = 0.67), with the value shifting the equation closer to ratio dependence than to pure prey dependence. Values much closer to the extreme cases for two species of invasive crabs (m = 0.9 for Carcinus maenas and m = 0.1 for Hemigrapsus sanguineus) were also found (Griffen and Delaney 2007). These authors suggest that the strength of predator dependence can be specific to different predator species.…”

Section: Modelmentioning

confidence: 64%

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Functional responses modified by predator density

et al. 2008

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Realistic functional responses are required for accurate model predictions at the community level. However, controversy remains regarding which types of dependencies need to be included in functional response models. Several studies have shown an effect of very high predator densities on per capita predation rates, but it is unclear whether this predator dependence is also important at low predator densities. We fit integrated functional response models to predation data from 4-h experiments where we had varied both predator and prey densities. Using an information theoretic approach we show that the best-fit model includes moderate predator dependence, which was equally strong even at low predator densities. The best fits of Beddington-DeAngelis and Arditi-Akçakaya functional responses were closely followed by the fit of the Arditi-Ginzburg model. A Holling type III functional response did not describe the data well. In addition, independent behavioral observations revealed high encounter rates between predators. We quantified the number of encounters between predators and the time the focal predator spent interacting with other individuals per encounter. This time "wasted" on conspecifics reduced the total time available for foraging and may therefore account for lower predation rates at higher predator densities. Our findings imply that ecological theory needs to take realistic levels of predator dependence into account.

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Section: Modelmentioning

confidence: 64%

“…Very few studies measured functional responses directly on a demographic time scale and accounted for prey depletion in their analysis. Among such rare exceptions that investigated predator dependence in natural populations are the studies by Vucetich et al (2002), Jost et al (2005) and Griffen and Delaney (2007).…”

Section: Introductionmentioning

confidence: 99%

Functional responses modified by predator density

et al. 2008

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“…Negative interactions between these species are common (Jensen et al 2002;Griffen 2006;Griffen and Byers 2006b), and the spread of dense H. sanguineus populations has apparently caused the disappearance of C. maenas from most rocky intertidal habitats in Long Island Sound (Lohrer and Whitlatch 2002a;Kraemer et al 2007). H. sanguineus populations in the Gulf of Maine are also on the rise and a similar species replacement may be in progress in these northern regions (Griffen and Delaney 2007).…”

Section: Study Systemmentioning

confidence: 87%

“…The more recently introduced crab, H. sanguineus, was first noted in New Jersey in 1988, spread quickly, and now ranges from central Maine to North Carolina (McDermott 1998). Populations of this new invader are often very dense, and a recent survey of 30 sites throughout New England found that mean densities of H. sanguineus were approximately six times higher than current and historic C. maenas densities (Griffen and Delaney 2007). Recent studies imply that H. sanguineus may have broad impacts on the native community (Tyrrell and Harris 1999;Ledesma and O'Connor 2001;Bourdeau and O'Connor 2003;Brousseau and Baglivo 2005), as well as large species-specific effects on bivalve prey (Lohrer and Whitlatch 2002b).…”

Section: Study Systemmentioning

confidence: 99%

“…First, negative interactions between these species can alter their impacts in areas where they still coexist (Jensen et al 2002;Griffen 2006;Griffen and Byers 2006b;Griffen and Byers 2006a;. Second, the densities of each species vary widely, with maximum H. sanguineus densities that are many times higher than C. maenas densities (Lohrer and Whitlatch 2002a;Griffen and Delaney 2007). Further, density-dependent intraspecific interference is stronger for C. maenas than for H. sanguineus (Griffen and Delaney 2007).…”

Section: Study Systemmentioning

confidence: 99%

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Community impacts of two invasive crabs: the interactive roles of density, prey recruitment, and indirect effects

Griffen

Byers

2008

Biol Invasions

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Assessing the implications of species invasion for native communities requires determining whether effects of invaders are novel, or are redundant with effects of species that are already present. Using a pair of field experiments conducted over two successive years, we examined factors that influence community impacts of a recent predatory crab invader (Hemigrapsus sanguineus) and a previously established invasive crab (Carcinus maenas) on New England coasts. We demonstrate that effects of these species differ temporally with changes in the ambient prey community, and are influenced by density differences between the two species and by different strengths and types of indirect effects that each elicits. Our study highlights the importance of including bottom-up processes (i.e., prey recruitment) when examining the redundancy of consumers.

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Spatially variable habitat quality contributes to within‐population variation in reproductive success

Griffen

Norelli

2015

Ecology and Evolution

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Variation in habitat quality is common across terrestrial, freshwater, and marine habitats. We investigated how habitat quality influenced the reproductive potential of mud crabs across 30 oyster reefs that were degraded to different extents. We further coupled this field survey with a laboratory experiment designed to mechanistically determine the relationship between resource consumption and reproductive performance. We show a >10-fold difference in average reproductive potential for crabs across reefs of different quality. Calculated consumption rates for crabs in each reef, based on a type II functional response, suggest that differences in reproductive performance may be attributed to resource limitation in poor quality reefs. This conclusion is supported by results of our laboratory experiment where crabs fed a higher quality diet of abundant animal tissue had greater reproductive performance. Our results demonstrate that spatial variation in habitat quality can be a considerable contributor to within-population individual variation in reproductive success (i.e., demographic heterogeneity). This finding has important implications for assessing population extinction risk.

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Species Invasion Shifts the Importance of Predator Dependence

Cited by 59 publications

References 48 publications

Functional responses modified by predator density

Functional responses modified by predator density

Community impacts of two invasive crabs: the interactive roles of density, prey recruitment, and indirect effects

Spatially variable habitat quality contributes to within‐population variation in reproductive success

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